Cytocentric Visionaries: Roger Rönn

This is a five-part series of blog posts containing excerpts from an interview that Dr. Alicia Henn, Chief Scientific Officer of BioSpherix, conducted with Roger Rönn, who is finishing his PhD at Lund University. Our conversation on methods for decreasing reactive oxygen species in HSC cells was edited for brevity and clarity.

In the last post, Roger told us about his shock at finding extremely high ROS levels in HSC in culture. Today we talk about controlling ROS in culture.

What ways have you identified to decrease ROS in HSC?

RR: I have found four different ways, each through a completely unique mechanism. I’ve used neutralization of ROS using antioxidants as one strategy. When cells feel stressed, no matter what the stressor may be, they will actually produce ROS directly. It’s a vicious cycle, reactive oxygen species can cause stress to a cell but also directly result from stress itself. That’s the second strategy, inhibiting a stress signaling pathway.

The third approach is blocking innate immunity. We have a heterogeneous collection of cells in our cultures. We have mature macrophages and granulocytes, cells that can release large amounts of ROS into the extracellular space if activated. I’m using a pharmacological blocker for that process.

The fourth strategy is trying to reduce ROS that form spontaneously from the high concentration of oxygen that we have. Until recently, we have always used a standard culture condition for our cells. Most people culture their cells at 21% O₂, the same concentration that we breathe. This is also referred to as normoxia – and this is something that has bugged me for some time- there is nothing normal with what we call normoxia.

Normoxia is not a good term?

RR: If you actually measure the O₂ concentration in your blood stream and in the different regions of the body, it’s very low. It’s between underneath 1% to 3%. You can say that when you have anything at such a high O₂ concentration, it’s an increased probability that these things will actually oxidize spontaneously- rust, in a sense. So what I did as my fourth strategy, I was changing the O₂ condition from our standard 21% down to 4%, closer to a physiologic level. So you can say it’s like a normalization of the abundance of O₂.

The combined effort of these four strategies can keep more than 50% of our cells in the ROS-low domain. And when you compare hematopoietic progenitors and HSC-like cells, separated into the ROS-low and ROS-high, there is a superior functional capacity in the ROS-low fraction compared to the ROS-high. In fact when you look at the HSC-like fraction there is almost no functional capacity whatsoever, in terms of how much the cells can grow, in the ROS-high fraction.

So what does that mean for HSC culture?

RR: We have evidence that the ROS we have with our standard culture conditions, to a very large extent, is responsible for functional degeneration of hematopoietic cells and progenitors that we create in the lab. I think this is an important thing, because as long as we continue to ignore the impact of increased ROS, if we believe the previous work of others, we can’t expect to produce functional HSCs. I think that unless we fix this, we might never be successful.

In the next post, Roger discusses with us factors that might keep researchers from acting to protect their cells from ROS in vitro.

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 Roger Rönn interview: Part 1, Part 2, Part 3, Part 4, Part 5